Rear Axle confusion

[Mac1984]

Hi all,

I am finally a proud owner of a smiley transit again..

Its a 1998 TD, with single wheel axle 5 stud and a 4.56 ratio..

So far I have replaced the rear drums and breakshoes due to excessive wear, I might have to do the
Brake cylinders too, as she is still a bit unsteady when breaking.. Didn't have much time recently but will do more during the summer.. As I would prefer a more cruising friendly axle ratio, I'm thinking of swapping the diff or the axle..

I'd prefer to swap the whole axle with one that has rear discs, but I'm not sure if that has been done before?

Of course I went through the search, and it seems it has been tried but nothing been mentioned about the outcome?
Also some people seem to say mk3 3.89 axle is not interchangeable at all, some say the diff alone can be swapped ( if u find one, that is)

But I have been left a bit confused as about a newer axle from a mk6 or 7 or whatever can be fitted to the smiley?

Apologies in advance if I have missed the right answer..

So basically I am thinking of fitting an axle with rear discs and a better ratio to the smiley.. Its a camper BTW and I am not using it for towing at all, so its not an issue to me..

Thanks for all advice from you experts out there...